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DAY 4 Considerations for Interpretation Bias Participation Rate Reversed Time Order. EPI CHALLENGE Proposal Form Considerations for Interpretation Participation Rate. - PowerPoint PPT Presentation
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DAY 4
Considerations for Interpretation
Bias
Participation Rate
Reversed Time Order
1
EPI CHALLENGEProposal Form
7. Considerations for InterpretationParticipation Rate
7b. Describe what the term “participation rate” means, and explain why it is important to know it. Use a formula or diagram if you wish.
Explain how you will calculate the participation rate for your study.
EPI Challenge
Master Proposal Form
Name of Team Member
________________
EPI CHALLENGEProposal Form
7. Considerations for InterpretationRepresentativeness
7c. Describe why representativeness is important in the interpretation of your study results.
Develop an additional question for your survey that will help your team determine the representativeness of the group of students that participated in your study.
EPI Challenge
Master Proposal Form
Name of Team Member
________________
EPI CHALLENGEProposal Form
7. Considerations for InterpretationBias and Reversed Time Order
7d. Describe one form of bias that might influence the possible association between your exposure and outcome.
7e. Describe how reversed time order might affect your interpretation of study results.
EPI Challenge
Master Proposal Form
Name of Team Member
________________
6
One possible explanation for finding an association is because the exposure causes the outcome.
Because observational studies are complicated by factors not controlled by the investigator,
other explanations also must be considered, including, confounding,
bias, and reversed time order.
Big Epi Idea
7
One possible explanation for finding an association is because the exposure causes the outcome.
Because observational studies are complicated by factors not controlled by the investigator,
other explanations also must be considered, including, confounding,
bias, and reversed time order.
Big Epi Idea
8
Bias
9
Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the outcome
Bias
10
Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the outcome
Bias
In a x-sectional study,
what do we call the
estimate of an
exposure’s effect on
the outcome?
11
9010
9010
b
d
a
c
Total
Exposure
No Exposure
OutcomeNo
Outcome
Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the outcome
Outcome Prevalences
Prevalence Ratio
BiasIn a x-sectional study,
what do we call the
estimate of an
exposure’s effect on
the outcome?
60%
20%
12
9010
9010
b
d
a
c
Total
Exposure
No Exposure
OutcomeNo
Outcome
1
Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s
effect on the outcome
Outcome Prevalences
Prevalence Ratio
Bias
50%
50%
13
9010
9010
b
d
a
c
Total
Exposure
No Exposure
OutcomeNo
Outcome
.5
Any systematic errorin the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the outcome
Outcome Prevalences
Prevalence Ratio
Bias
25%
50%
14
9010
9010
b
d
a
c
Total
Exposure
No Exposure
OutcomeNo
Outcome
2
Outcome Prevalences
Prevalence Ratio
Bias
50%
25%
Any systematic errorin the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the outcome
15
16
A flaw in measuring exposure or outcome data that results in different quality of data between comparison groups
Information Bias
17
A flaw in measuring exposure or outcome data that results in different quality of data between comparison groups
Information Bias
18
9010
9010
b
d
a
c
Total
Alcohol
No Alcohol
Birth Defect
1
A flaw in measuring exposure or outcome data that results in different quality of data between
comparison groups
Outcome Prevalences
Prevalence Ratio
Information Bias
No Birth
Defect
5%
5%
19
9010
9010
b
d
a
c
Total
Alcohol
No Alcohol
Birth Defect
1
A flaw in measuring exposure or outcome data that results in different quality of data between
comparison groups
Outcome Prevalences
Prevalence Ratio
Information Bias
No Birth
Defect
5%
5%
20
9010
9010
b
d
a
c
Total
Sports Participation
No Sports
Participation
High GPA
3
Outcome Prevalences
Prevalence Ratio
Information Bias
Low GPA
60%
20%
A flaw in measuring exposure or outcome data that results in different quality of data between
comparison groups
21
9010
9010
b
d
a
c
Total
Hyper Texting
No Hyper
Texting
Low GPA
1
Outcome Prevalences
Prevalence Ratio
Information Bias
High GPA
30%
30%
A flaw in measuring exposure or outcome data that results in different quality of data between
comparison groups
22
A flaw in measuring exposure or outcome data that results in different quality of data between comparison groups
Information Bias
Systematic error due to differences in the accuracy and completeness of the recall to memory of past experiences
Recall Bias
23
A flaw in measuring exposure or outcome data that results in different quality of data between comparison groups
Information Bias
Systematic error due to differences in the accuracy and completeness of the recall to memory of past experiences
Recall Bias
24
Recall Bias
25
9010
9010
b
d
a
c
Total
Exposure
No Exposure
OutcomeNo
Outcome
1
Systematic error due to differences in the accuracy and completeness of the recall to memory of past experiences
Outcome Prevalences
Prevalence Ratio
Recall Bias
30%
30%
26
9010
9010
b
d
a
c
Total
Stress
No Stress
4
Outcome Prevalences
Prevalence Ratio
Recall Bias
Birth Defect
No Birth
Defect
8%
2%
Systematic error due to differences in the accuracy and completeness of the recall to memory of past experiences
27
28
Error due to systematic differences in characteristics between those who take part in a study and those who do not
Selection Bias
29
9010
9010
b
d
a
c
Total
Exposure
No Exposure
OutcomeNo
Outcome
1
Error due to systematic differences in characteristics between those who take part in a study and those who do not
Outcome Prevalences
Prevalence Ratio
Selection BiasDid Not
Participate
Did Participate
25%
25%
30
9010
9010
b
d
a
c
Total
Marijuana
No Marijuana
Low GPA
1
Outcome Prevalences
Prevalence Ratio
High GPA
Error due to systematic differences in characteristics between those who take part in a study and those who do not
Selection BiasDid Not
Participate
Did Participate
25%
25%
31
9010
9010
b
d
a
c
Total
More Sleep
Less Sleep
More Physical Activity
4.7
Outcome Prevalences
Prevalence Ratio
Less Physical Activity
Did Not Participate
Did Participate
Error due to systematic differences in characteristics between those who take part in a study and those who do not
Selection Bias
66.7%
14.3%
32
One possible explanation for finding an association is because the exposure causes the outcome.
Because observational studies are complicated by factors not controlled by the investigator,
other explanations also must be considered, including, confounding,
bias, and reverse time order.
Big Epi Idea
33
Non-response is a particular problem affecting cross-sectional studies and can result in bias of the measures of outcome.
From Epi Textbooks
35
The number of completed survey instruments divided by the total number of persons who would have been surveyed if all participated.
Usually expressed as a percentage.
Participation Rate
36
Results
The completed interview rate for adolescents was 48%.
Participation Rate
37
Results
The completed interview rate for adolescents was 48%.
What do you want your response rate to be?
Participation Rate
What did the
investigators
need to do
in order to
calculate their
participation rate?
38
The completed interview rate for adolescents was 48%.
Results
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Xxxxxx, Xxxxxx, Xxxxxx, Xxxxxx, Xxxxxx
EPIC Summer Session 2 Presentations
June 26, 2015
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
What will you
need to do
in order to
calculate your
participation rate?
Calculate Your Participation Rate
39
40
A representative sample resembles the population from which it was taken in some way.
Representative Sample
Non-response is a particular problem affecting cross-sectional studies and can result in bias of the measures of outcome.
From Epi Textbooks
Non-response is a particular problem affecting cross-sectional studies and can result in bias of the measures of outcome. This is a particular problem when the characteristics of non-responders differ from responders.
From Epi Textbooks
43
Representativeness of Participants
Are the 48% who participated similar or dissimilar to those who were invited to participate?
Results
The completed interview rate for adolescents was 48%.
What could the
investigators
have done to get
a sense of the
representativeness
of the participants
in their
investigation?
44
Results
The grade levels of the adolescents invited to participate were 25% freshmen, 25% sophomores, 25% juniors, and 25% seniors.
Representativeness of Participants
The grade levels of the adolescents who did participate were 25% freshmen, 25% sophomores, 25% juniors, and 25% seniors.
Are the 48% who participated similar or dissimilar to those who were invited to participate?
45
Results
The grade levels of the adolescents invited to participate were 25% freshmen, 25% sophomores, 25% juniors, and 25% seniors.
Representativeness of Participants
The grade levels of the adolescents who did participate were 40% freshmen, 30% sophomores, 20% juniors, and 10% seniors.
Are the 48% who participated similar or dissimilar to those who were invited to participate?
46
Results
The distribution of the schools among possible SS1 survey participants was 20% Cedar Cliff, 20% John Harris, 20% Lower Dauphin, 20% Middletown Area, and 20% Sci Tech
.
EPIC Summer Session 1 Survey
Wednesday, June 23, 2014
The answer to
what question
from our SS1
survey could be
used to get a
sense of the
representativeness
of the SS1
participants who
completed the
survey?
Representativeness of Participants
Are the XX% who participated similar or dissimilar to those who were invited to participate?
The distribution of the schools among the actual SS1 survey participants was 20% Cedar Cliff, 20% John Harris, 20% Lower Dauphin, 20% Middletown Area, and 20% Sci Tech
.
47
Results
The distribution of the schools among possible SS1 survey participants was 20% Cedar Cliff, 20% John Harris, 20% Lower Dauphin, 20% Middletown Area, and 20% Sci Tech
.
EPIC Summer Session 1 Survey
Monday, June 23, 2014
Representativeness of Participants
Are the XX% who participated similar or dissimilar to those who were invited to participate?
The distribution of the schools among the actual SS1 survey participants was ___% Cedar Cliff, ___% John Harris, ___% Lower Dauphin, ___% Middletown Area, and ___% Sci Tech
.
48
The completed interview rate for adolescents was 48%.
Results
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Xxxxxx, Xxxxxx, Xxxxxx, Xxxxxx, Xxxxxx
EPIC Summer Session 2 Presentations
June 26, 2015
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
What question
can you include
in your survey
so that you can get
a sense of the
representativeness
of your participants?
Representativeness of Participants
49
50
One possible explanation for finding an association is because the exposure causes the outcome.
Because observational studies are complicated by factors not controlled by the investigator,
other explanations also must be considered, including confounding,
bias, and reversed time order.
From Epi Textbooks
Egg Chicken
51
Which happened first?
52
A cross-sectional study is a study in which exposure and outcome are measured simultaneously in a given population or a sample of that population. This study can be thought of as providing a "snapshot" of the frequency of an exposure and outcome at a particular point in time. Data that are collected as part of a cross-sectional study can be used to assess the prevalence of an outcome. Also called a prevalence study.
Cross-Sectional Study
Cross-sectional studies are carried out to investigate possible associations between hypothesized exposures and outcomes.
From Epi Textbooks
Cross-sectional studies are carried out to investigate possible associations between hypothesized exposures and outcomes. They are limited, however, by the fact that they are carried out at one time point and give no indication of the sequence of events — whether exposure occurred before, after or during the onset of the outcome.
From Epi Textbooks
Cross-sectional studies are carried out to investigate possible associations between hypothesized exposures and outcomes. They are limited, however, by the fact that they are carried out at one time point and give no indication of the sequence of events — whether exposure occurred before, after or during the onset of the outcome. This being so, it is impossible to infer causality.
From Epi Textbooks
Cross-sectional studies are carried out to investigate possible associations between hypothesized exposures and outcomes. They are limited, however, by the fact that they are carried out at one time point and give no indication of the sequence of events — whether exposure occurred before, after or during the onset of the outcome. This being so, it is impossible to infer causality. Nevertheless, cross-sectional studies can indicate associations that may exist and therefore are supportive of continuing to investigate hypotheses with other study designs.
From Epi Textbooks
57
4 Basic Epidemiological Study Designs
58
A situation in which the hypothesized time order of an exposure and an outcome is actually reversed and the “outcome” actually comes before the “exposure.”
Reversed Time Order
59
Family MealsGood
Mental Health
Family Meals Associated with Good Mental Health
X-Sectional Study
60
Obesity Watching TV
Obesity Linked to Watching TV
X-Sectional Study
61
9010
9010
b
d
a
c
or
or
Total
More Sleep
Less Sleep
More Physical Activity
5
Outcome Prevalences
Prevalence Ratio
50 50
10 90
100
100
100
100
50
10
Less Physical Activity
50%
10%
More Sleep Associated with More Physical Activity
62
More Sleep
More Physical Activity
More Sleep Associated with More Physical Activity
X-Sectional Study
63
Spanking Aggression
Spanking and Aggression
X-Sectional Study
64
Violent Video Games Can Increase Aggression
65
Violent Video Games
Aggression
Violent Video Games Can Increase Aggression
Playing violent
video games
often may well
cause increases
in aggressive
behavior.
X-Sectional Study
66
... the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems.
Epidemiology
67
Violent Video Games
Aggression
Violent Video Games Can Increase Aggression
Playing violent
video games
often may well
cause increases
in aggressive
behavior.
It could be that … highly aggressive individuals are especially attracted to violent video games.
“… the control of health problems.”
X
X-Sectional Study
68
Violent Video Games
Aggression
Violent Video Games Can Increase Aggression
Playing violent
video games
often may well
cause increases
in aggressive
behavior.
It could be that … highly aggressive individuals are especially attracted to violent video games.
X
“… the control of health problems.”
X-Sectional Study
69
A cross-sectional study is a study in which exposure and outcome are measured simultaneously in a given population or a sample of that population. This study can be thought of as providing a "snapshot" of the frequency of an exposure and outcome at a particular point in time. Data that are collected as part of a cross-sectional study can be used to assess the prevalence of an outcome. Also called a prevalence study.
Cross-Sectional Study
71
One possible explanation for finding an association is because the exposure causes the outcome.
Because observational studies are complicated by factors not controlled by the investigator,
other explanations also must be considered, including confounding,
bias, and reversed time order.
From Epi Textbooks
72
A cross-sectional study is a study in which exposure and outcome are measured simultaneously in a given population or a sample of that population. This study can be thought of as providing a "snapshot" of the frequency of an exposure and outcome at a particular point in time. Data that are collected as part of a cross-sectional study can be used to assess the prevalence of an outcome. Also called a prevalence study.
Cross-Sectional Study
73
Cross-Sectional Study
• Difficult to determine whether the outcome followed exposure in time or exposure resulted from the outcome.
• Not suitable for studying rare outcomes or outcomes with a short duration.• As cross-sectional studies measure prevalent rather than incident cases,
the data will always reflect determinants of survival as well as etiology.• Susceptible to bias due to low response and misclassification due to recall
bias.
Limitations
74
Cross-Sectional Study
• Relatively quick and easy to conduct (no long periods of follow-up)• Data on all variables are only collected once• Able to measure prevalence for all factors under investigation• Multiple outcomes and exposures can be studied
Strengths
75
"There must be something in the coffee."
4 New Mothers with 6 Babies in Strollers
Which happened first?
77
Which happened first?